Airplane insulation

[Andreas Warberg]

Hi guys

We are doing a physics project in school concerning the thermodynamics
of flight and I have some questions I was hoping you could help me
with.

I need to estimate how much heat is lost from the cabin to the outside
when flying at 10000m. I have calculated the approximate outside
temperature given the sea-level temperature but I don't know how planes
are insulated!
It is my impression that the hull is typically made of an exterior
aluminum skeleton followed by the insulation and finally the inner
cabin wall. In this setup the main insulation effect will probably come
from the insulating material.
I expect the insulation to be at least as good as the ones used in
modern buildings but I don't know how much of it is used - can you give
me some examples of the width of the insulation please?

Thank you in advance.

Best regards
Andreas

[Robert M. Gary]

I would be surprised if its nearly as good as what is in building
walls. The insulation on aircraft is much thiner (at least much thiner
than the madated insulation for new buildings here in California). The
insulation I've seen is between 1/2" and 1" thick compared to 5" or so
that you see in modern buildings.

-Robert

[Andreas Warberg]

Thanks for you reply.

That is surprising!
Is it your impression that this applies to most (commercial) airplanes?
If not, can you give me an example of an airplane with an insulation
thickness like that?

Best regards
Andreas

[pgbnh]

At least for most General Aviation aorcraft, the primary purpose of fuselage
insulation is for sound deadening, not for heat loss.
The insulation is typically closed cell foam, with some level of fire
protectant.
I suspect that what you will find of insulating value in most small aircraft
will be (from inside out):
1. A liner - cloth or vinyl, often padded (maybe 1/4 inch thick)
2. Then maybe one inch of air space
3. Then 1/2 inch insulation
4. Then exterior aluminum (or fabric)

MUCH less insulating capability than a modern building.

I think you will find a much higher level of insulation in larger aircraft,
but again, not likely approaching a building
"Robert M. Gary" > wrote in message
oups.com...
>I would be surprised if its nearly as good as what is in building
> walls. The insulation on aircraft is much thiner (at least much thiner
> than the madated insulation for new buildings here in California). The
> insulation I've seen is between 1/2" and 1" thick compared to 5" or so
> that you see in modern buildings.
>
> -Robert
>

[Jim Logajan]

"Andreas Warberg" > wrote:
> It is my impression that the hull is typically made of an exterior
> aluminum skeleton followed by the insulation and finally the inner
> cabin wall. In this setup the main insulation effect will probably come
> from the insulating material.
> I expect the insulation to be at least as good as the ones used in
> modern buildings but I don't know how much of it is used - can you give
> me some examples of the width of the insulation please?


This URL provides some fuselage design considerations:
http://adg.stanford.edu/aa241/fuselayout/fusesection.html

This quote should get you in the ballpark (I presume you can assume the
entire thickness contains insulation for the purpose of this assignment):

"Finally, the fuselage frame, stringers, and insulation thickness must be
added to determine the fuselage outer diameter. Typically, the outer
diameter is about 8% larger than the cabin diameter."

Also, it appears some McDonnell Douglas aircraft use metalized Mylar
insulation.

[Robert M. Gary]

> Also, it appears some McDonnell Douglas aircraft use metalized Mylar
> insulation.

At least in the GA world most of us are getting rid of our old
insulation for modern materals to avoid rust. The old insulation may
hold moisture which will eat the plane.

-Robert

[Jim Macklin]

Airplanes that fly at 10000 meters have jet engines that
heat air as a function of just running [ P3 or bleed air] to
temperatures above 1,000 F. This highly compressed hot air
is manipulated and used for heating and cooling. The use of
insulation is limited because of weight and to an extent
because of bulk. Airplanes will have 1/4 to 1/2 inch
(6mm-13 mm) of a fireproof material. Sound as well as heat
insulation are functions of the material.

Aircraft ventilation causes a complete change of cabin air
every 5-10 minutes, so insulation is not a function, they
just dump 100,000s of BTU into the cabin.


--
James H. Macklin
ATP,CFI,A&P

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"Andreas Warberg" > wrote in
message
oups.com...
| Thanks for you reply.
|
| That is surprising!
| Is it your impression that this applies to most
(commercial) airplanes?
| If not, can you give me an example of an airplane with an
insulation
| thickness like that?
|
| Best regards
| Andreas
|